Why would copper level drop in QT?

[Punchanello]

This has happened a few times over the last few days. It hasn't happened to me before.

I am using a hob power filter with a seeded sponge. No other filter media. No sand or rock.

I have added an air stone. Could this cause it?

 

[ngoodermuth]

If the air-stone is porous, maybe a little... how big of a drop are you seeing? I can’t imagine an air stone being a big enough surface to make a huge difference.

Picture of the QT in question?

 

[mfinn]

I think I read here on R2R that even sponge will absorb copper.
I dealt with pretty significant drops in copper in my quarantine tank while using several sponge filters.
Now it's the opposite. I removed all the sand ( for wrasses ) and am trying to get the copper levels down, but it's not easy.

 

[Big G]

This has happened a few times over the last few days. It hasn't happened to me before.

I am using a hob power filter with a seeded sponge. No other filter media. No sand or rock.

I have added an air stone. Could this cause it?

I've noticed that during the warmer months or when my home is being heated, there seems to be a bit of copper loss perhaps during evaporation a bit of the copper follows the water molecules into the air. Would be interesting to test the evaporate for any concentrations of copper.

 

[Punchanello]

Here's a photo.

As best as I can make out I'm losing about .05ppm a day.